Within information technology, the term upstream refers to the flow of data, says Joe Brockmeier in a recent Red Hat blog. “An upstream in open source is the source repository and project where contributions happen and releases are made. The contributions flow from upstream to downstream.”
A familiar example, Brockmeier says, is the Linux kernel, “which is an upstream project for many Linux distributions. Distributors like Red Hat take the unmodified (often referred to as "vanilla") kernel source and then add patches, add an opinionated configuration, and build the kernel with the options they want to offer their users.”
The upstream serves as the focal point for code contributions, bug fixing, collaboration, and decision making that then propagates to other open source projects.
As Brockmeier says, “Each upstream is unique, but generally the upstream is where decisions are made, the contribution happens, and where the community for a project comes together to collaborate for the benefit of all parties.”
Read the complete article at Red Hat.